[R] Problems with scan

From: David C. Howell <David.Howell_at_uvm.edu>
Date: Tue, 04 Nov 2008 13:34:46 -0700


I have been having problems with using scan(). I searched the archives and found someone with the same problem several years ago, but did not find a solution.

I want to prompt the user for input, scan in that input, and then go on to use it as a variable.

The simplest version of my program is

cat("enter m","\n")
m <- scan(n = 1, quiet = T)
m

If I enter these lines one at a time, they work perfectly and I get the following output, which is just want I want..
> cat("enter m","\n")

enter m
> m <- scan(n = 1, quiet = T)
1: 24
> m

[1] 24
>

However if I submit the three lines together, as you would when running a program, I get

> cat("enter m","\n")

enter m
> m <- scan(n = 1, quiet = T)
1: m
1:
Error in scan(file, what, nmax, sep, dec, quote, skip, nlines, na.strings, :
  scan() expected 'a real', got 'm'
>

In this case the program is reading the line after the scan function as the input to scan, rather than pausing for my entry. The help archives suggested putting this as a function "e.g., getn()" but that gives the same result.

The scan help file doesn't address this and the help archives don't give me what I need. How do I cause the program to wait for keyboard entry from me?

I am running version 2.8 on a Windows machine, but the problem goes back to much earlier versions.

While I'm asking, is there a way to suppress the echoing of lines? I would like to omit the lines above that begin with ">". I cannot find "echo" using help.search and can't think of another name to search under.

Thanks,

Dave Howell

-- 
David C. Howell
PO Box 770059
627 Meadowbrook Circle
Steamboat Springs, CO
80477

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Received on Tue 04 Nov 2008 - 20:38:15 GMT

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